(a) Technical Field
The present invention relates to an organic silica master batch elastomer for a tire, which comprises a specific organosilicon compound and silica organically surface-modified by a silane coupling agent, and a preparation method thereof.
(b) Background Art
In general, in the process of manufacturing tires, tire threads are fabricated by mixing rubber and filler in a mixer. As for the rubber, styrene butadiene copolymer and conjugated diene based rubber are used, and as for the filler, carbon black or silica is used alone or in combination as a reinforcing material.
Silica is an environment-friendly material. In recent years, with far more strict environmental regulations and rapidly increasing oil prices, silica has been spotlighted as a tire filler, and its use is on rapid increase. However, when silica is used as a reinforcing material, silica particles may aggregate with each other due to inter-particular interaction to form large-sized particles, which results in problems in mixing with rubber and dispersion of silica itself. Since dispersion of silica in rubber has much impact on the wear and life of tires, it is very important to maximize dispersibility of silica.
Occasionally, a master batch type elastomer is used by mixing with carbon black in order to improve dispersibility of reinforcing material and simplify tire manufacturing process. However, when a silica master batch type elastomer is prepared from a diene based copolymer prepared by solution polymerization, most of silica is lost by water during steam stripping because silica is hydrophilic. Therefore, there has been much limitation in the preparation of silica master batch type elastomer through solution polymerization in commercial scale. In addition, when hydrophobic silica is used as a tire reinforcing material, it is difficult to attain the mechanical properties required for a tire because chemical bonding with rubber is impossible.
Various researches have been carried out for the development of the use of silica for maximizing its dispersibility. For example, U.S. Pat. No. 5,925,713 discloses a technique of improving affinity to a filler through modification using a monomer having an epoxy group, and Korean Unexamined Patent Publication Nos. 94-019797 and 94-019795 disclose examples of improving wear resistance and impact resistance at low temperature by dispersing polymethylsiloxane in composition.
In addition, various researches have been performed in order to improve of silica through modification by introducing terminal groups to rubber. But, these approaches are restricted in improving dispersibility of a filler. Some silica manufacturers have introduced a technique of preparing a silica master batch elastomer comprising rubber and general-use silica using a specially designed apparatus. However, silica is not sufficiently dispersed in the rubber mixture. Further, when such prepared mixture is used to manufacture a tire, there are problems associated with processability and production because of the increase of Mooney viscosity [DKT 2006 Poster 33, “Rubber Filler Composition based on Solution Polymers and Silica—Status of Developments”].
A technique of improving compatibility with rubber using hydrophobic silica is introduced in WO 1998/37015 (Korean Patent Laid-open No. 2000-0075614). The use of hydrophobic silica results in improved compatibility with rubber. But, modulus, tensile characteristics and wear characteristics of tire deteriorate significantly because of difficulty in chemical bonding with rubber.
Korean Patent Laid-open No. 2002-0021407 discloses a method of preparing a tire material in the form of silica or carbon black master batch by mixing silica or carbon black in rubber latex prepared by emulsion polymerization. However, with a copolymer prepared by emulsion polymerization, it is difficult to attain low rolling resistance, high wet resistance and low heat generation required for a high-performance tire.
Ultimately, in order to satisfy the physical properties required for such silica tire, a silica master batch type elastomer prepared from conjugated diene or vinyl aromatic copolymer prepared by solution polymerization has to be used.
Until now, a technique by which a silica master batch type elastomer can be developed using a commercial solution polymer is unavailable.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.